1. Field of the Invention
The present invention relates to a solid-state image-sensing device in which variations in sensitivity among individual pixels are corrected for.
2. Description of Related Art
In recent years, in the field of solid-state image-sensing devices having photoelectric conversion elements such as photodiodes, there have been proposed solid-state image-sensing devices that output an electrical signal obtained by natural-logarithmically converting the amount of incident light (for example, see JP-A-H11-313257). In such logarithmic-conversion solid-state image-sensing devices, variations in threshold voltage among individual MOS transistors for logarithmic conversion produce variations in sensitivity among individual pixels, and eventually produce fixed-pattern noise components among pixels.
As an improvement, there have been proposed logarithmic-conversion solid-state image-sensing devices that use, as calibration noise data for correcting actually sensed images, sensed-image data obtained under irradiation with uniform light.
With these logarithmic-conversion solid-state image-sensing devices that use, as calibration noise data for correcting actually sensed images, sensed-image data obtained under irradiation with uniform light, however, the calibration noise data cannot be acquired by ordinary image sensing. Thus, to correct for variations in sensitivity among individual pixels on a real time basis, one frame worth of sensed-image data under irradiation with uniform light need to be acquired and stored in a frame memory. Moreover, variations in temperature and other conditions cause variations in sensitivity among individual pixels, and therefore, to correct for variations in sensitivity among individual pixels on a real time basis in the presence of variations in temperature and other conditions, sensed-image data obtained under irradiation with uniform light need to be previously acquired under different temperature and other conditions. Thus, to store sensed-image data obtained under different sets of conditions, the frame needs to be given a large capacity.